Michael Cortez - Academia.edu (original) (raw)
Related Authors
University of North Carolina at Chapel Hill
Uploads
Papers by Michael Cortez
Using a Lotka-Volterra model, we explore how the indirect interactions between two predators are ... more Using a Lotka-Volterra model, we explore how the indirect interactions between two predators are altered by interspecific competition between two shared prey. We identify when different indirect interactions arise between the predators, classifying interactions by predator responses to (1) slightly increased mortality in the other predator, (2) a slightly decreased population of the other predator, or (3) removal of the other predator. When interspecific prey competition is low, all methods predict negative indirect effects between predators, i.e., competitive interactions. Strong and/or highly asymmetric interspe-cific prey competition often produces at least one positive indirect effect between predators, i.e., mutualism or contramensalism. However, the three methods often disagree about the strength of and signs characterizing the indirect effects between predators, including cases where all three methods predict a qualitatively different interaction. These differences arise for a variety of reasons, including hydra effects (where a predator increases in abundance with increased mortality) and extinction of prey species following the removal of one predator. We also show that cyclic dynamics do not arise in our model when there is a single predator, but under strong interspecific prey competition, the indirect interactions between two predators can drive cyclic community dynamics. Similar phenomena are likely to occur in other food webs, and understanding them will be required to predict the impact of environmental change on the abundances of species in those webs.
Using a Lotka-Volterra model, we explore how the indirect interactions between two predators are ... more Using a Lotka-Volterra model, we explore how the indirect interactions between two predators are altered by interspecific competition between two shared prey. We identify when different indirect interactions arise between the predators, classifying interactions by predator responses to (1) slightly increased mortality in the other predator, (2) a slightly decreased population of the other predator, or (3) removal of the other predator. When interspecific prey competition is low, all methods predict negative indirect effects between predators, i.e., competitive interactions. Strong and/or highly asymmetric interspe-cific prey competition often produces at least one positive indirect effect between predators, i.e., mutualism or contramensalism. However, the three methods often disagree about the strength of and signs characterizing the indirect effects between predators, including cases where all three methods predict a qualitatively different interaction. These differences arise for a variety of reasons, including hydra effects (where a predator increases in abundance with increased mortality) and extinction of prey species following the removal of one predator. We also show that cyclic dynamics do not arise in our model when there is a single predator, but under strong interspecific prey competition, the indirect interactions between two predators can drive cyclic community dynamics. Similar phenomena are likely to occur in other food webs, and understanding them will be required to predict the impact of environmental change on the abundances of species in those webs.